您好，我正在尝试在网格中的许多不同空间点对我的函数施加特定条件。然而，我正在复制大量代码，而且它变得越来越低效。
如何通过简单地使用 do 循环来完成我需要做的事情？我试图对我的函数施加的特定条件在所有不同的空间点上都是相同的，因此我认为有一种方法可以在单个循环中完成所有这些操作。或者如何将所有这些 If/else if 语句组合成一个语句？一定有比我正在做的更有效的方法。
我在下面提供了示例代码。
FUNCTION grad(psi)
IMPLICIT NONE
INTEGER :: i,j,kk,ll
INTEGER, PARAMETER :: nx = 24, ny = 24
COMPLEX,DIMENSION(3,3,-nx:nx, -ny:ny) :: psi, grad
REAL :: pi
REAL :: f0
INTEGER :: nxx, nyy
nxx = nx/2
nyy = ny/2
pi = 4*atan(1.0)
f0 = pi**2*1.3
DO i=-nx+1,nx-1 !spatial points
DO j=-ny+1,ny-1 !spatial points
IF ( i == 0 .AND. j == 0 .AND. i == j) THEN ! I have lots of statements like this
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE IF ( i == nxx .AND. j == nyy .AND. i == j) THEN ! I have lots of statements like this
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE IF ( i == -nxx .AND. j == -nyy .AND. i == j) THEN ! I have lots of statements like this
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE IF ( i == nxx .AND. j == -nyy) THEN ! I have lots of statements like this
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE IF ( i == -nxx .AND. j == nyy) THEN
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE IF ( i == nxx .AND. j == ny) THEN
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE IF ( i == -nxx .AND. j == ny) THEN
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE IF ( i == nx .AND. j == -nyy) THEN
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE IF ( i == nx .AND. j == nyy) THEN
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j) - f0*psi(kk,1,i,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j) - f0*psi(kk,2,i,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j) - f0*psi(kk,3,i,j)
END DO
ELSE
DO kk=1,3
grad(kk,1,i,j) = psi(kk,1,i+1,j)
grad(kk,2,i,j) = psi(kk,2,i+1,j)
grad(kk,3,i,j) = psi(kk,3,i+1,j)
END DO
END IF
END DO
END DO
END FUNCTION grad
